[FEATURE]: Exclusion constraints

### Describe what you want

There doesn't seem to be a way (nor any ticket) about generic [exclusion constraints](https://www.postgresql.org/docs/current/ddl-constraints.html#DDL-CONSTRAINTS-EXCLUSION) in the documentation.

This would be a great add.
I can, of course, work around this with a manual migration, but always nicer to have this constraint in code :)

No repository files, tests, or entry points are named. Start by reading the linked PostgreSQL exclusion-constraint documentation and then locate the project's existing constraint support to determine the API and migration behavior that need extending. Done means generic exclusion constraints can be represented in code and applied through migrations.

Written by the indexing model from the issue text.